Air pollution 'raises risk of death after MI'

Thousands of patients with previous MI are dying prematurely due to high air pollution levels, a UK study suggests.

MI patients face an increased risk of death from long-term exposure to pollution
MI patients face an increased risk of death from long-term exposure to pollution

Researchers found that long-term exposure to man-made air pollution after an MI greatly increases the risk of dying within four years of hospital admission.

They said thousands of lives could be saved each year if patients reduced their exposure to heavily polluted air. Academics urged doctors to warn patients with prior MI about the risk and to be aware of measures of air quality where they live.

A team from the London School of Hygiene and Tropical Medicine looked at the medical records of 154,204 patients who had been admitted to hospital for acute coronary syndrome (ACS) in England and Wales over four years. During this time there were 39,863 deaths. 

Researchers linked patients' outcomes to the average air pollution concentration where they lived, and accounted for other factors such as age, sex, medical history, smoking status, income and employment.

They found that exposure to particulate matter (PM) 2.5µm in diameter or less was associated with all-cause mortality among patients that had a been admitted to hospital with ACS. For every 10µg/m3 increase in PM2.5 there was a 20% rise in the death rate.

Patients living in London had the highest exposure to PM2.5 compared to other parts of the country.

The authors estimated that the mortality rate would be reduced by 12%, or 4,783 deaths, if the patient cohort had been exposed to natural levels of PM2.5.

Lead author Cathryn Tonne from London School of Hygiene and Tropical Medicine in London said: ‘While reducing levels of PM2.5 will lead to increased life-expectancy and is an important public health priority, it isn’t likely to reduce socioeconomic inequalities in prognosis very much. There are likely to be other factors that are more important than PM2.5 exposure in explaining socioeconomic inequalities in prognosis, and this requires further investigation.’

In an accompanying editorial, Professor Pier Mannucci, director of the IRCCS Ca’ Granda Maggiore Policlinico Hospital Foundation, Italy, said clinicians should inform patients of this risk and encourage them to be aware of media alerts on air quality where they live.

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